Having listened to the Python Site (Thanks for the pointer!), I reckon it's played in Bflat, which makes it more interesting to play, though you could cop out and transpose it into A to make it easier. Just busking you can get away with A, A7, D, E and E7. I'm about to add it to my repertoire, so if I get round to it, I'll post a fuller version in due course.

"Buddy can you spare a dime" is a good guitarist's challenge - I recall Chris Newman doing a storming version. For another, dig out Peter Paul and Mary's "Whatshername" from Album 1700. It's a really elegant descending sequence that's quite straightforward when you suss it out.